1. Field of the Invention
The present invention relates to a flat panel display device, and more particularly, to a method of manufacturing a flat panel display device with an enhanced sealing structure.
2. Description of the Related Technology
In general, flat panel display devices such as organic light emitting panel display devices and TFT-LCDs can be made thin and flexible, and thus, many studies are being conducted in the related technology.
Organic light emitting display devices deteriorate as moisture penetrates within, so that a sealing structure for preventing penetration of moisture is required.
Conventionally, a metal can or a glass substrate has been used as a sealing member of OLED elements. The metal can or glass substrate may contain desiccant powder for absorbing moisture from the OLED elements once it is sealed. Alternatively, a desiccant film may be attached using, e.g., a double-sided tape as the sealing member. In either case, the sealing member is combined with a substrate, on which a light emitting element is formed, using a UV hardening sealant or a thermosetting sealant.
However, the use of a desiccant powder complicates the manufacturing process of flat panel display devices, increases the material and manufacturing costs, and increases the thickness of the substrate. Furthermore, due to the area being filled with the desiccant powder, front emission or double-sided emission may not be achievable, particularly when the sealing member comprises a non-transparent substrate.
U.S. Pat. No. 5,882,761 discloses an organic light emitting display apparatus including a stack of a pair of opposing electrodes with an emissive layer made of an organic compound, a container sealing the stack from external air, and a desiccant placed inside the container, wherein the desiccant remains in a solid state even after absorbing moisture. This patent suggests use of alkali metal oxide, sulfate, etc., as the desiccant.
When a desiccant film is used as the sealing member, there is a limit in preventing penetration of moisture, and the desiccant film may be damaged during manufacture or during use of the sealing member. Thus, the durability and reliability of the desiccant film are not sufficiently high, and therefore, the use of desiccant film is not suitable for mass-production.
Japanese Patent Laid-open Publication No. 5-335080 discloses a method of forming a protective layer in a thin, organic light emitting display including an emissive layer containing at least one kind of an organic compound between an anode and a cathode, at least one of which is transparent, the protective layer being made of amorphous silica.
A sealant for combining a sealing member with a substrate has a low resistance to pressure, and its resistance to moisture penetration is lowered, thereby degrading a sealing effect.
Due to the problems discussed above, glass frit with a high resistance to pressure and a good sealing characteristic has been suggested for use as a sealant. However, the glass frit needs to be softened by laser melting However, a laser scanning device for softening cannot be disposed under a nitrogen or vacuum atmosphere for sealing, and thus the glass frit cannot be practically exploited.